Compost: a feast of nutrients for your garden. A simple process keeps plants healthy and green

Six consecutive days of rain here recently left ponds overflowing, rivers in flood - and garden soils leached of their available nutrients. A popular TV garden show was quick to reveal the effects of this rain-induced deficiency as closeup shots showed tomato plants with a distinctly yellowish cast to their leaves. ''Feed them to revive them'' was the show's message for the week.

My own garden soil, so light that water sinks right in even even during downpours, is considered particularly vulnerable to this leaching. Even so, my tomatoes and peppers were a rich, dark green - testimony to that marvelous commodity we call compost.

Composted plants aren't immune, but they are not nearly as vulnerable to starvation as are chemically fed plants after heavy rains. While rain may leach away some of the immediately available nutrients, the bacteria and other organisms within the compost immediately set about making more nutrients available.

That's the nature of compost. With the help of soil organisms it goes on steadily releasing nutrients until it is all used up. This is the reason, too, why compost always performs far better in the garden than a simple chemical analysis of its available nutrients says it should.

This past spring I dug a hole, threw in a shovelful of compost, replaced the topsoil, and planted the tomatoes. It was a hasty operation, done with no great care, but the tomatoes didn't seem to mind. The compost was only half decomposed at the time and was made in the simplest fashion by throwing waste materials (principally kitchen scraps, with some leaves and occasionally a little newspaper) all winter long into a compost bin.

All this shows that composting requires no great skill on the gardener's part , and that partial decomposition is perfectly acceptable to the plants. Many studies suggest that the greatest benefit is gained by returning spent crop residues directly to the soil, largely duplicating what takes place in the wild. But this isn't always convenient in the garden and not always wise when it comes to disposing of food wastes that are particularly rich in plant nutrients.

So we turn to composting. Decay of surface litter in the wild is slow and involves no heat buildup. Composting, on the other hand, is much more rapid, and the frenzied activity within the pile frequently results in some very high temperatures.

Compost, then, is no more a product of nature than a loaf of bread or a slice of your favorite pie. While they involve natural ingredients and natural processes, they also require the manipulative hand of man.

In composting, man is required to gather up the basic materials, mix them with air and water, include a little activator, and place them in a pile of sufficient bulk to hold onto the resulting heat.

The activator is a protein-rich product such as manure, bone meal, blood meal , alfalfa meal, cottonseed meal, fresh lawn clippings, dry dog food, and the like. In the absence of these materials, fertile soil will help. You also can use a commercial fertilizer, but studies show that this is not as effective as a natural product.

The nitrogen-rich materials add spark to the compost pile by feeding the bacteria, which multiply prolifically and, in turn, tackle the rest of the waste , converting it to useful fertilizer.

Begin a compost heap with a 4- to 6-inch layer of waste. Sprinkle on the activator and enough water to moisten the materials, and add more waste. Keep repeating this layering process as the organic materials become available.

To get the most rapid breakdown, turn the pile to get a fresh supply of air into the mix every other day. But that's a lot of work and most of us aren't in that much of a hurry, anyway.

Composting will take place without oxygen but it takes a whole lot longer. Too, if the airless heap is disturbed at any time during this process, chances are it will smell abominable. So turning the pile periodically helps a lot, but you can get a good supply of air into the pile simply by sticking in a garden fork and wiggling it around a little.

There is also a dandy little aerator tool on the market that I use - a compost aerator that has a rod with a handle at the top and two hinged paddles at the bottom. As you push the rod into the compost, the paddles fold up against the rod, offering little resistance. Then, as you withdraw the stick the paddles automatically open, pulling some of the compost with them. This not only mixes the organic matter but creates new passages for air and moisture to penetrate. I've seen this tool offered in several seed and garden catalogs.

Keeping the compost pile neat and tidy-looking is important, particularly when you haven't a grove of trees to hide it in. Commercial compost bins (there are several makes on the market that look like barrels with holes in the side for aeration) are good as well. Hardware cloth or snow fencing, arranged in a circle at least three feet in diameter, also works effectively.

I place my compost bins directly on the ground, which makes it simple for the earthworms to get in. Then when I find a few worms in every forkful, I calculate the compost is ready for the garden.

There is an exception to this practice, however. If the pile is to be placed in the shade of a tree, first place a piece of plastic film over the ground. This prevents the tree from feeding on the compost you want your cauliflowers to dine on.